Rotary die cutting machines (not shown in the drawings) have been publicly known. In these types of cutters a frame is used to provide powered rotation to a die cut cylinder and an anvil cylinder. A blanking die, which may be provided in sections, is attached to the die cut cylinder to form a blanking die roll and rotated together with the anvil cylinder. The rotary die cutting machine is commonly used in the manufacture of cartons or boxes to trim or otherwise cut corrugated paperboard stock to desired shapes, provide them with apertures and cutouts. Cutting is performed by a cutting rule that extends radially outwardly from the blanking die roll.
The rotary die cutting machine die roll may also include at least one and usually a plurality of blocks of so-called “scrap ejection” and “material separation” rubber. The rubber blocks are mounted upon and extend outwardly from the curved surface of the die boards which comprise the die roll, at advantageous locations and often closely adjacent to various cutting rules. In their uncompressed condition the rubber blocks project radially outwardly, and often beyond the height of the toothed cutting edge of the cutting rule. The rubber blocks may be compressed as they pass into and through the close space between the die roll and the anvil cylinder. As they pass from such close spaced relationship, the rubber blocks return outward movement to help separate the freshly cut corrugated fiberboard sheet product from the areas occupied by the cutting rule. Where a hole is cut, for example, the cutting rule will be arranged in a somewhat continuous closed line to form an enclosed cut. The rubber blocks are especially helpful in removing the freshly cut corrugated fiberboard sheet product from these shapes of cutting knives.
The use of rubber blocks is insufficient to assist scrap rejection in a high speed Rotary die cutting machine. Even where a clean cut takes place, and even with many precise feed controls and the like, in both low speed and high speed rotary die cutters the process of cutting out a portion of the rejection of scrap needs more control. In some dies an ejector mechanism is used, which is a cantilevered arm having a pivot connected first end and a second end extending partially behind the die blade and which has limited movement to assist in dislodging scrap. In some cases the cantilevered arm receives an assist from within the die cut cylinder and communicating through the blanking die with a cam mechanism. In other die cut cylinders, an ejector mechanism may rely upon centrifugal force, or interaction with the anvil cylinder (either a rebound action or a positive compression action), and may also use springs or other rubber blocks. The number of combinations and configurations to provide an “assist” to scrap rejection are many.
Even with finely tuned reactive structures assisting in the rejection of scrap, the certainty with which this scrap material is eliminated as soon as possible after it is cut from corrugated fiberboard sheet is not yet achieved. Corrugated fiberboard sheet scrap may be unintentionally carried with the corrugated fiberboard sheet product to a stacking machine downstream from the operation of the anvil cylinder and blanking die roll.
The scrap can make its way into the sheets of cut material in one of two ways. The first way for it to make it into the sheets of cut material is for an incomplete cut to occur. The completeness of cut can be adjusted by adjusting the pressure and penetration of the cutter into the passive polymeric roller, as well as by periodic sharpening of the cutting rules. The second, and traditionally less controllable way that scrap can make it into the finished product is by failure of the scrap to be rejected from within the cutting rule.
The presence of scrap within cut cardboard is costly and hazardous. Where the presence of scrap is prominent enough to cause the producer of the cut cardboard to visually notice it, it results in additional handling, and more personnel than would otherwise be needed. Where the scrap is present in the die cut and stacked cardboard, it disrupts further handling machinery. Further handling machinery may include box assembly, box manipulation and filling and box closure and sealing. Most of the automated processes which act upon die cut and stacked cardboard involve vacuum pickup devices which rely upon vacuum cups to cleanly abut and engage the die cut stacked cardboard for lifting, manipulation, repositioning and the like. One small piece of scrap can prevent vacuum engagement and cause a machine to jam.
The most expensive and highest speed processing types of machinery have a higher reliance upon a consistent product feed stock which can be engaged consistently at high speed and speedily manipulated. The presence of scrap within cut cardboard can result in high numbers of ruined constructed structures or can cause the machinery to shut down until repaired. Where capacity of final production machinery is high, even a 10 minute shut down can result in significant loss of production. A thirty second malfunction can ruin high numbers of products resulting a significant waste.
Corrugated fiberboard sheet scrap may therefore eventually wind up within the corrugated fiberboard sheet product, carton, box or processed the like formed in the die cutting operation. Unwanted scrap downstream of the die cutting process can have very undesirable consequences, particularly when the carton or box is used for foods, such as pizza, which can be contaminated by the scrap paperboard. Scrap contamination of the carton or box can also ensue when the blocks of product ejection rubber do not extend rapidly enough, as they exit from space between the die roll and anvil cylinder of the apparatus, to prevent the paperboard stock from advancing beneath the trimmed scrap, and then being transported by the cut paperboard stock to the packing machine.
Proper rejection means that the cutting rule area should be able to reject the scrap just after cutting occurs and after the cut sheet moves on to the remainder of the cutting process, but before the cutting rule is brought back into contact with a fresh area of material to be cut. Any scrap which remains within the cutting rule will be doubled at the next cutting cycle. Doubling can cause scrap to be transmitted to the final product by forming an incomplete cut. An incomplete cut can cause a “shad” effect and draw scrap into the finished product. Doubling can also cause scrap to remain within the blade area over several cutting cycles.
Correct operation dictates that each piece of die-cut scrap be held only long enough for the processed sheet material to pass away from the cutting die without any entrained scrap, and for any scrap within the cutting die to be rejected and expelled as soon as possible after clearing the processed sheet in order that the cutting die be “emptied” and ready for the next cutting operation. Because there are so many variables, including die size, blade depth, ejector action, and especially paper type, surface and corrugation, finding a solution which works to broadly contribute to a significant reduction of the possibility of the rejection of scrap outside of the desired range of operation of the die wheel, has not heretofore been devised.